How do I prevent ice dams in this area in the future?
House is in North Central NJ, zone 4a, 2×4 construction, built 2005-6, ~4500 sq ft, insulated with batt insulation, unfinished and unconditioned attic with gable, ridge, and soffit vents. We are not the original owners so didn’t have a say in the design or build specs but there are clearly lots of elements that run counter to many of the views espoused here e.g. complicated roof design, 2nd floor heating/cooling unit and duct work in attic, house not air sealed or as insulated as it could be for a modern home, etc. That said, we like the house and area and plan to make some improvements.
We’ve had significant water infiltration from ice dams in one area (see pics): between the right garage roof (roof over the kneewall in our bedroom extension) and the left facing wall of the study near the area where the rotted trim was removed. One potential solution is to improve the insulation in several locations to limit heat transfer to that section from below (the garage), from the kneewall, and from the study. Our bedroom is above the garage and I’m considering options there including even taking down the garage ceiling (double layer of 5/8 gypsum unfortunately) and spraying foam under the joists. As you can see from the tarps on the roof, we recently had damage to the roof from a tree falling and will need to reframe a section of roof over our bedroom. I’m considering taking this opportunity to alter the roof design to limit the accumulation of snow in that recessed triangular area. I’m trying to think about how best to insulate any new roof structure and also thinking about the issue of rain water draining from several roof planes. It is difficult to design adequate gutter drainage so I was also wondering about adding an underground roof that I read about here (https://www.greenbuildingadvisor.com/blogs/dept/green-communities/underground-roof) in addition to improving the grading near the foundation to help promote flow of water away from the foundation. Finally, although I’m not sure how relevant this is to the current issue, since there no communication of this area with our attic, I’m looking at ways of bringing the attic into the thermal envelope of the house, probably via insulating under the rafters, but thought I would make that the topic of another post.
I was hoping to get some feedback on the sketches below, and certainly willing to entertain other ideas from readers here. These are the only sketches I have right now, but I might be able to add additional views in the next few days. Here are some comments from our architect about these:
Option 1 – Extend the main hip roof to the left. This would require extending the small lower plate roof into it, and also constructing a cricket. The only way to make this look somewhat reasonable would be to extend the office/study wall left to fill the void (not pictured).
Option 2 – Extend the secondary master hip roof forward towards the street, maintaining the same pitch as the existing roof. The pro is the roof is the same pitch as that over the master bedroom. The con is that it leaves a portion of the rake of the roof exposed when looking at it from it from the front door.
Option 3 – Extend the secondary master hip roof forward towards the street, using a pitch that goes exactly from the existing fascia to the intersection of the garage roof and office wall. The pro is the aesthetics and ability to shed water effectively. The only con is that the pitches are different although I don’t think anyone would be able to perceive this. I would just want to make sure there was proper underlay to minimize any damage to shingles at the transition point.
Thanks for your advice and apologies for the long post.
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